The present invention broadly relates to infeeding and outfeeding substantially flat products arriving in an imbricated or shingled formation and pertains, more specifically, to a new and improved apparatus for forming a gap in an imbricated stream of substantially flat products, particularly printed products.
Generally speaking, the apparatus of the present invention is of the type comprising a first conveyor driven at a first conveying speed, at least one second conveyor arranged downstream of the first conveyor as viewed in a predetermined product conveying direction, and a gap-forming device arranged between the first conveyor and the at least one second conveyor. The gap-forming device comprises first conveying means and second conveying means extending substantially parallel to the latter, whereby the first conveying means are drivable substantially at the first conveying speed for the purpose of conveying the imbricated product stream supplied by the first conveyor to the at least one second conveyor. For the purpose of forming a gap in the imbricated product stream, one of the two conveying means is drivable at a second conveying speed which is higher with respect to the first conveying speed, in order to feed the products located at the beginning of gap formation at the region of the gap-forming device to the at least one second conveyor, and the other one of the two conveying means is drivable at most at the aforesaid first conveying speed, in order to take over and further convey the products supplied by the first conveyor.
An apparatus for forming a gap in an imbricated stream of substantially flat products is known, for example, from German Patent No. 2,852,603, published Oct. 23, 1980 and its cognate British Patent Application No. 2,037,714, published Jul. 16, 1980. The cardboard sheet stacking apparatus disclosed therein comprises a separating station or gap-forming unit provided between a first conveyor and a second conveyor. The separating station consists of an endless conveyor belt for feeding the sheet flow coming in an imbricated formation from the first conveyor to the second conveyor, the endless conveyor belt being always driven at the same speed as the second conveyor. Coaxially with the reversing or deflection rolls of the endless conveyor belt, there are arranged chain wheels over which an endless chain runs, one run length of which carries louvre strips. In the normal case, i.e. when no interruption in the sheet flow is required, the endless chain is not in operation and the strips are not in the conveying-active run of the endless conveyor belt. When the provision of a gap in the imbricated sheet flow becomes necessary, the endless chain is driven at a speed which corresponds to the speed of the first conveyor. The louvre strips coming into the upper run section lift the sheets arriving from the first conveyor and thereby separate them from the sheets on the conveyor belt. At the same time, the drives of the endless conveyor belt and the second conveyor have been stepped up to a higher speed, so that the sheet-flow section on the endless conveyor belt is cleared away. Due to the fact that the endless conveyor belt and the second conveyor run at increased speed, the necessary gap occurs in the sheet flow. The increased speed of the endless conveyor belt and of the second conveyor is successively reduced to the original slower speed as soon as the last sheet of the separated sheet-flow section leaves the respective belt. The cardboard sheets lying on the louvre strips are supplied at unvaried speed to the second conveyor and the endless chain is further driven until the louvre section is no longer at the region of the conveying-active run. The cardboard sheets following the louvre section are fed to the second conveyor by means of the endless conveyor belt driven at the original speed thereof.
An apparatus for subdividing a continuous stream of overlapping paper sheets into a succession of discrete sections of equal length while avoiding a change of overlap of the products in an imbricated array is known, for example, from Swiss Patent No. 660,353, published Apr. 15, 1987 and its cognate U.S. Pat. No. 4,585,227, granted Apr. 29, 1986. This known apparatus comprises a first conveyor which is structured as a belt conveyor and driven at a constant first speed. The discharge end of the first conveyor is adjacent to the receiving end of a second conveyor likewise structured as a belt conveyor, the length of which is at least equal to the length of a section of the stream of overlapping paper sheets. At the end region of the first conveyor there is provided an accelerating device comprising an endless chain conveyor which is adjacent and parallel to the conveying-active run of the first conveyor and carries a flexible elastic portion in the form of a rubber pad, the length of which approximately matches the length of the upper conveying-active run of the endless chain conveyor. The level of the upper conveying-active run of the endless chain conveyor is selected in such a manner that the rubber pad invariably extends into the path which is defined by the upper conveying-active run of the first conveyor while such pad advances in the stream conveying direction. The accelerating device and the second conveyor are driven by a variable-speed motor at the constant first speed of the first conveyor, or at a second speed which exceeds the constant first speed. The accelerating device and the second conveyor are driven at the constant first speed until the entire rubber pad is located in the path which is defined by the conveying-active run of the first conveyor. During this period the paper sheets infed by the first conveyor are passed on to the second conveyor and conducted away by the latter at the constant first speed. The trailing end of the rubber pad having now entered the aforesaid path, the endless chain conveyor of the accelerating device and the second conveyor are accelerated to run at the higher second speed. As a result, the paper sheets lying on the rubber pad and the paper sheets lying on the second conveyor are co-accelerated, and the paper sheets lying on the rubber pad are fed to the second conveyor without a change of the mutual overlap. There is thereby formed a gap between the last sheet on the rubber pad and the next following sheet as viewed in the sheet conveying direction. The speed of the motor is reduced back to the constant first speed when the trailing end of the formed section has advanced beyond the discharge end of the first conveyor. This state-of-the-art apparatus is provided for subdividing a continuous stream of overlapping sheets or for separating discrete sections of a selected length from the leader of a stream of sheets, but is not suitable for forming gaps at any random locations or any predetermined locations within an imbricated product stream.
A further apparatus for forming a gap within the imbricated stream or flow of substantially flat products is disclosed, for example, in German Patent Application No. 3,831,742, published Jun. 22, 1989. This known apparatus comprises two horizontally arranged transport belts driven at the same speed. The delivery end of the first transport belt slightly overlaps the receiving end of the second transport belt, so that the products supplied by the first conveyor descend onto the second conveyor and form a new imbricated formation for further conveyance on the second conveyor. The gap-forming device comprises a perforated belt or tape which is arranged between laterally spaced belts of the second conveyor and revolvingly driven at a lower speed with respect to the speed of the transport belts. The perforated belt or tape is provided with sections of suction holes and guided over a suction trough. In order to form a gap in the aforesaid new imbricated formation, the perforated belt is driven at the aforesaid lower speed, so that the products descending into the tape section with the suction holes are held or retained at the perforated belt or tape and further conveyed with the following descending products at the lower speed, while the leading products downstream of the tape section provided with the suction holes are conveyed at unchanged speed by means of the second conveyor and form thereby the gap. At the region of the perforated belt or tape during the gap-forming operation, the overlap of the aforesaid new imbricated stream of products is increased. As soon as the suction holes depart from the region of the suction trough, all products arriving from the first conveyor are again conveyed at the same original speed.